This invention relates to a reflection type electro optical device and a projection type display apparatus using the same. The electro optical device includes a twisted liquid crystal layer and utilizes a birefringence effect of a liquid crystal due to an electric field.
There have been two kinds of prior art reflection type liquid crystal electro optical devices each of which utilize a twisted liquid crystal. One uses an optically uniaxial electro optical medium as a 1/4 .lambda. phase plate. The other is described in U.S. Pat. No. 4,019,807 and the Laid Open Patent No. 56-43681, wherein the liquid crystal with a twist angle of 45.degree. to the molecular axis receives a direct polarized incident light applied slantingly and transmits it as an elliptically polarized light without any reflection under no electric field or is subjected to a birefringence under an electric field.
However, in the prior art reflection type liquid crystal electro optical devices, there have been problems in that tolerance is small for the thickness of a liquid crystal layer and display performance varies easily. Also, since the output displaying uniformity is lowered and is an elliptically polarized light, the loss in light increases.
Accordingly, an object of the present invention is to provide a reflection type electro optical device which reduces light loss (hereinafter referred to .DELTA.nd) and much margin in manufacture by optimizing the twist angle, the product of layer thickness and birefringence, and the incident polarized light angle.
Furthermore, another object of the present invention is to provide a reflection type liquid crystal electro optical device in which the optical characteristics is sharp in response to an electric field and which liquid crystal responds sufficiently to a small variation in p.m.s. voltage, whereby a so-called multiplex driving is possible.
Still another object of the present invention is to provide a reflection type liquid crystal electro optical device having a large effective picture element area in comparison with prior art active element type liquid electro optical device with active elements, for example, thin film transistors (hereinafter referred to TFT's) and metal-insulator-metal elements (hereinafter referred to MIM's).
Further, still another object of the present invention is to provide a projection type display apparatus in which the optical arrangement is simple, light utilization ratio is large and color reproductivity is superior.